Herbert langwell



Sept. 15, 1931. H. LANGWELL 1,823,691

GRINDING OF CELLULOSIC MATERIALS Filed July 9. 192s retreated sept. 15, 19311 PATENT. oFFIcE HERBERT DANGWELL, or EPSON, ENGLAND, AssIeNoR To 'ooNmERcIAL soLvEN'rs conronATIoN, or TERRE HAUTE, INDIANA, A coRronATIoN or MARYLAND GRINDING or oELLULosIc MATERIALS Application led July 9,

The present invention relates to a methodl of grinding or comminuting various materials, and it is especially adapted to the grinding of cellulosic or plant material which pos-` sesses a relatively soft portion and a .relative- E ly hard and tough portion which normally w homogeneous ground product.

fermentation thereof, or forother purposes but it will be understood that the process may l be equally applied to any'cellulosic material of the nature above outlined; and, although d the grinding of corncobs is herein specically illustrated, nevertheless, this adaptationA is illustrative only.

fermentation products. of cellulose have so greatly increased that it has been found highly expedient, in view ofthe decreasing supply of the raw materials commonly employed` for these purposes, to seeka cheap andrelatively constant supply of cellulose, and in view of the fact thatcorn is one of the'principal staple crops of the United States, much investigation attended with marked success has been 'made of the Autilization of the 'cellulose of corncobs as asubstitute for Wood,v as a source of valuable products in high demand by the industries. 1 i y It may here be pointed out that the structure of a corncob consists of a soft outer layer surrounding a-hard, tough core, and that the etlicient fermentation ,of the cobsrequiresa relatively fine and homogeneous meal, which meal is vproduced by the grinding of the cobs. This grinding operation has heretofore normally been attended with-marked diiiculties': The hard, tough core prevents, normally, grinding .the cobs in rolls, as the rolls-become choked and blocked by the tough core; the grinding must therefore-be done by attrition, and the hard, tough core causes a veryhigh degree of wear upon the mills, and even then there is frequently not. an even grinding of the core material.' as its tendency is'to Hake instead of grinding to a meal.

' For heating these gases,

192s. serial No. 291,212.

The present invention seeks to'overcome these difculties of dry grinding by overcomingthe flaking tendency of the core, and rendering the ent1re cob thoroughly brittle,

thereby permitting the use of rolls in grind-vy ,1ng,4 and very materially reducing the wear .in attrition mills.

, The invention is predicatedupon the fact that dry cobs are brittle, the brittleness increasing with reduction of the moisture-content of the cobs. It has been found that if the cobs are substantially heated, but insufficiently to char them, and then ground while they-are in a substantially heated condition, lthe above objectsareattained, as the mois-` ture content is reduced to a low minimum by vthe heating, .and reabsorption ofimoisture'isl prevented. The cobs therefore have a maxi- Y v E mum degree of brittleness and can be readily In recent. years-industrial demands for reduced to ahomogeneous meal, .with a relatlvely low' power consumption. l i v In carrying 'out .the drying,'any t drler, which` may be convenient, can e111- ployed. The accompanyin drawing illustrates one form which has een found to be -eflcient, the single figure representing adiagrammatic sectionalview ofa vertical shaft type of kiln. y

y. Referring inA detail to the drawing, the kiln 1s generalyy indicated at 10,-'1a11d is provided with ports, 11, adapted toadmit heated gases for the carrying out of the d fng. there is provildyeld a stove, 12, conveniently heated; by burning coke, indicated at 13. It willbe understood thatany convenient type ofheater', and Aany convenient kind of fuel maybe employed in the place of the specific illustrated type of heater. In the illustrated installation, air maybe admitted to the stove or heater,'12, through the line, 14,.the line -conveniently branching, as indicated at 15 and 16, so'as to admit air above and below the coke bed, 13- as desired, dampers,17 and 18, being placed in the branches, 15 and 16, respectively, to.

charge being indicated by the numeral 19, this of air through the Stoveas charge being the cellulosic material or corncobs which are to bedried.

In operation, the cellulosic material or cobs are first `air dried, andl then, periodically charged into the top of the open shaft and re- 'moved from the base in equivalent amounts so as to keep a constant depth of charge in the shaft. A cokeire in the stove, 12, supplies hot flue gases which, when mixed with an excess of cold a1r introduced through thef branch, 15, to give a mixture of gases at, say

. 110 C., are blown through the charge in the shaft in a direction opposite to the movement of the charge at such a rate that moisture is not deposited on the cold newly `chargedmaterial at the top of the shaft. Precautions should be taken to revent-.sparks from the lcoke fire reaching t e charge and firing it.

The charge is introduced into the mill for grinding while hot, absorption'of moisture eing thereby prevented.

As a specific-illustration of the process as appliedto the grinding of corncobs, thefollowing example is given:

A'batch of steam-dried cobs which had been.

sults ofthe grind were as follows:

Run number 1. 2

160-180 C. 240 Iba/hr.

Temperature of cobs Rate of grinding Screen analysis o! product:

` `On 8 mmh On 14 mmh 0n m mesh On 28 mesh 0n 48 m'esh g 0n 100 mmh Through 100 mesh These results indicate an increased grinding capacity of approximately 20% when the cobs are hot.

The hot lglrinding acts u on the cobs when they have t eir maximum egree of fragility,

.and increases the advantages of dry grinding, as there is no possibility of reabsorption of moisture and the moisture content Vof the hot cobs is the absolute minimum which is possible. Before dry grinding was applied.

to corncobs, wet digestion processes were tried but were abandoned for the dry grinding process on account of the ditliculty of wet grinding and the trouble which the nlp sometimes caused in the fermenter. Ta ing into consideration the cost of digestion, the trouble in handling and grinding wet material, and the complication due to, furfural andslimy washes, wet grinding has been discontinued in favor of. dry grinding. The dry grinding avoided these diiiiculties, although in the latter there is somewhat of an increase in the power consumption required, owing to the structure of the cobs; and also, it was extremely difficult to get a uniformly ground meal. These disadvantages are largely overcome through the application of hot grinding, as herein described.

'With respect to dry grinding of cobs, the

following procedure and data are illustrative of this process:

:Five batches of cobs of apparently different moisture content were selected. These were each put through a preliminary Crusher, and then a weighed amount of each batch was run through a ne pulverizer. Each batch was carefully weighed and scrubbed before and after going through the pulverizer. The time 'of grinding was observed. Moisture was -determined on the samples going to the pulverizerv and screen analyses were made on the pulverizel` product. Thecobs are nearly dried in passing through the pulverizer.

Sample No 1 2 3 4a 4b Deseripton. Dry cobs. Damp. Wet. Very wet. Very wet. Weight before grind 501bs 50 50 50 50 Weight a it e r grindin 48 do .46' 43 38 38 Time of grinding 28min.... 43 60 105 99 Screen analyses:

0n 8 mesh-. 26% 35 33 20 19 0n 14 mesh 26% 31 28 38% 40 0n m mesh- 12% -10 9% 10 12% 0n 28 mesh- 11% 7 8% 7 9% on 48 mesh. 13% e 9% 1o 934 Through 100 mesh 6 3 6 6 3 Residue- 5 4 5 8 7 Per cent H10 (wet basis) 5. 3% 1i 14. 6 26. 5 27. 4

Calculations Sample No 1 2 3 4a 4b Very Very Deseription Dry cobs. Dam Wet. wet. wet.

A (5% H10) (11g:l (14.6% (26.5% (27.4%

- H1 H10) H10) 11,0) Mill temperal warm. warm. warm cold. warm.

GrindingJ rate wet o0 s 1071bs./hr. 70 50 28% 30% Grindin rate -dry eo s 101lbs./hr. 62 43 21 22 LbsJhr. through 8 mesh 74% 40 29 17 i8 Lbs. per hrs.

through v 20 mesh. 35 17 12% 5% 6% From the above data, 'it will be seen that the grinding rate very rapidly increases with the reduction of the moisture content of the cobs. For Wet cobs having a moisture content of 20%, the grinding rate will be about 35 lbs. per hour; reduction to 10% moisture .increases the grinding rate to 75 lbs. per hour;v and reduction to.5% gives a grinding rate of 107 lbs. cob (95% of 10 ture present).

This shows, therefore, that the rate of grinding of such materials as corncobs is per hour, or 101 lbs. of actual lbs., sincethere is 5% moisgreatly increased through reduction of the imately 180 C. until the moisture content is moisture coutent; and the grinding of the reduced to below approximately 5%,and then cobs While hot gives the maximum grinding immediately grinding the cobs before subeiicieney. This is of importance in any constantial cooling thereof.

nection where a uniform meal is desired, and In testimony whereof I atlix my signature.

the time factor is of importance.

it will be understood that the above speciie examples are illustrative only of the invention, and that it is desired to comprebend within the scope of this invention such modifications and changes as may be necessary to adaptit to varying conditions and uses.

What is claimed is:

1. process of grinding cellulosie material which comprises heating the material sufciently high to expel the moisture therefrom but avoi fr substantial charring, and then immediately grinding the said material before substantial cooling thereof.

2. A process of grinding corncobs Whic comprises heating the cobs to a tem rature ranging from approximately 110: to approm'mately 180 C. until substantially all moisture is expelled, and then immediately grinding the cobs before substantial cooling thereof. Y

3. A process of grinding corncobs which comprises heating the cobs suiiciently high to expel the moisture therefrom but avoiding substantial charring, and then immediately grinding the said material before substantial cooling thereof.

L. la process of grinding oellulosic material whichcomprises heating the material to a temperature ranging from approximately C. to approximately 180 C., until substantially all moisture is expelled, and then immediately grinding the material before substantial cooling thereof.

5. process of grinding cellulosic material which comprises heating the material sut'ciently high to reduce the moisture content of said material to below approm'mately 5% but-avoiding substantial charring, and then immediately grinding the said material before substantial cooling thereof.

6. process of grinding corncobs which vcomprises heating said cobs suiciently high ythe said material before substantial cooling thereof.

S. i process of grinding corncobs which comprises heating the 'oobs to a temperature range from approximately 110 C. to approx- HEBERT LANGWELL. 

